Fertility preservation before rectal cancer treatment
There is one decision in the whole course of rectal cancer treatment that cannot be postponed and cannot be taken again later: fertility preservation. Once pelvic radiotherapy has started, the window has closed for good.
This article is aimed particularly at young patients, in whom the incidence of rectal cancer is rising. It contains concrete numbers, because this is the kind of decision that is better made with data than with impressions.
Something that is said far too rarely
In an American study of 148 rectal cancer survivors diagnosed before the age of 50, more than half said their doctor had never discussed the effects of treatment on fertility with them. Only about one in five had frozen sperm, oocytes or embryos. One in five men and almost one in six women did not even know the option existed.
This is not a criticism of doctors. The moment of diagnosis is crowded: staging, MRI, surgery and stomas all have to be discussed. Fertility feels like a problem for afterwards. The trouble is that afterwards is too late.
The guidelines are explicit. ASCO requires that the risk of infertility be discussed at the time of diagnosis, and that interested patients be referred to a reproductive specialist before oncological treatment begins. In practice, fewer than half of oncologists make that referral routinely, and surgeons — often the first to see the patient — start the conversation in only 22-25% of cases.
If you are under 50 and you want children, ask yourself, even if nobody has raised the subject.
Radiotherapy is the problem, not chemotherapy
This is the most important idea in the article, and it is counterintuitive.
The chemotherapy used in rectal cancer — 5-fluorouracil, capecitabine and oxaliplatin in the FOLFOX and CAPOX regimens — is classified by the guidelines as low gonadotoxic risk. It is far gentler than the alkylating agents used in other cancers.
Pelvic radiotherapy is a different matter entirely. A Chinese study of 123 patients with colorectal cancer under the age of 40 compared the two situations directly:
- Rectal cancer, treated with chemoradiotherapy: about 94% persistent amenorrhoea
- Colon cancer, treated with chemotherapy alone: 4.2%
The same disease, the same type of chemotherapy. The difference is radiotherapy.
The practical conclusion: if you are told “your chemotherapy carries little risk for fertility”, the statement is true but profoundly incomplete. The right question is about radiotherapy.
What happens to the ovaries
Oocytes are among the most radiosensitive cells in the body. The dose that destroys half of the immature oocytes is under 2 Gy.
The dose that causes ovarian failure in almost all women falls with age, because the ovarian reserve is already smaller:
| Age | Sterilizing dose |
|---|---|
| 20 years | about 16.5 Gy |
| 30 years | about 14.3 Gy |
| over 40 years | about 6 Gy |
Long-course radiotherapy for rectal cancer delivers 45-50 Gy. Several times over the sterilization threshold, at any age.
The clearest study on this subject followed 76 women under 50 treated for locally advanced rectal cancer. The results:
- Without ovarian transposition, the mean dose received by the ovaries was 44.8 Gy
- With ovarian transposition, the dose fell to 1.7 Gy
- Every woman who did not have transposition became menopausal within the first 12 months. Without exception.
- Among those who did have transposition, 76% retained ovarian function
- No woman with an ovarian dose below 1.36 Gy developed ovarian failure
A single patient in the entire cohort carried a pregnancy — 15 years after treatment, with a premature birth at 25 weeks.
It is worth stating what we do not know as well: no study has measured the ovarian dose in short-course radiotherapy (5x5 Gy). By inference, if the ovaries are in the radiation field they receive a dose close to 25 Gy, which exceeds the sterilization threshold at any age. So the short course is not a gentler option for the ovaries — and, being delivered in a single week, it drastically compresses the time available for preservation.
The uterus: the problem transposition does not solve
This is the aspect most often left out.
Ovarian transposition moves the ovaries out of the radiation field. The uterus stays where it is. In the study cited above, the uterus received over 40 Gy in both groups — in the women with transposition and in those without.
The documented consequences of uterine irradiation: reduced uterine volume, myometrial fibrosis, impaired vascularization, damaged endometrium. Obstetric risks rise measurably even at low doses — premature birth becomes more frequent from 0.5 Gy onwards, and low birth weight from 2.5 Gy. Above 5 Gy, the risk of premature birth rises about 3.5 times, and that of low birth weight almost 7 times.
What this means in practice: a woman whose ovaries have been successfully transposed and who has frozen oocytes may still be unable to carry a pregnancy herself. In that case the only remaining route to a biological child is a gestational carrier — and surrogacy has no clear legal framework in Romania.
This is not an absolute bar, however. Normal pregnancies have been reported even after 54 Gy, and the European guideline explicitly mentions rectal and anal cancer among the situations in which pregnancy has been possible. The obstetric risk is nonetheless real and requires follow-up in a high-risk pregnancy service.
What happens in men
The testicles are not in the radiation field, but they receive scattered radiation, and the germinal epithelium is extremely radiosensitive.
Measured doses vary enormously — from 0.06 Gy up to over 14 Gy — depending on distance from the radiation field, field size, positioning and shielding. In one long-course radiotherapy series, 73% of men received over 2 Gy at testicular level, a threshold above which azoospermia often becomes permanent.
One important radiobiological detail: the testicle is one of the few organs in which fractionation makes the damage worse. The same total dose delivered over 25 sessions is more sterilizing than the same dose delivered all at once.
Radiotherapy also affects hormone production: after 46-50 Gy, testosterone falls by about 25%, and 35% of men remain below the lower limit of normal.
Surgery adds to this. In a prospective study of 207 patients operated on by total mesorectal excision for low rectal cancer, 82% of sexually active men developed ejaculatory disorders. Damage to the superior hypogastric plexus can cause retrograde or absent ejaculation — which makes natural conception impossible even if spermatogenesis is intact.
The good news: the testicular dose depends in part on planning. Gonadal shielding reduces the dose by over 66%. That is a question worth putting to your radiation oncologist.
The options and how long each one takes
| Method | Time required | Does it delay treatment? |
|---|---|---|
| Sperm freezing (1 sample) | a few hours | No |
| Sperm freezing (2-3 samples) | 5-7 days | Negligible |
| Testicular sperm extraction (TESE) | one procedure, same day | Negligible |
| Laparoscopic ovarian transposition | one procedure | Days |
| Ovarian tissue freezing | one procedure, no stimulation | Days |
| Oocyte or embryo freezing (“random start” protocol) | about 2 weeks | ~2 weeks |
For men, sperm freezing is cheap, fast and has no medical reason for delay. 2-3 samples 2-3 days apart are recommended, but a single sample is infinitely better than none. If a sample cannot be produced, testicular extraction is now considered standard of care. Important: collection must be done before any radiotherapy or chemotherapy, because sperm produced during treatment carries DNA damage.
For women, modern “random start” protocols allow stimulation to begin at any point in the cycle, without waiting for menstruation. That brings the duration down to about two weeks. The chances depend heavily on age: the cumulative live birth rate per case is about 64% under 35, 42% between 36 and 39, and 18% over 40.
Ovarian tissue freezing requires no hormonal stimulation at all — it is a single laparoscopy, schedulable within days. It is no longer considered experimental: the label was lifted in 2019, and since 2025 it figures among the established methods. One honest caveat for colorectal cancer: ovarian metastases occur in about 4-5% of premenopausal patients, so there is a theoretical risk of reintroducing malignant cells along with the graft. No cases of recurrence by this route have been reported, but the total experience is small.
Ovarian transposition: the option specific to rectal cancer
This one deserves the most attention, because it is the only intervention with proven efficacy in rectal cancer itself, and because it is a surgical procedure.
The ovaries are mobilized laparoscopically and fixed high and laterally, in the paracolic gutters, at least 4 cm from the radiation field. The lower border of each ovary is marked with radiopaque clips, so that the radiation oncologist can identify them on the planning CT — an essential detail that is frequently omitted.
The results: in a meta-analysis of 133 patients with rectal and anal cancer, 66.9% retained ovarian function, with a 30-day morbidity of only 1.2%. Efficacy depends strongly on age: about 90% under 40, compared with 38% over 40.
There are also ways it can fail, and they are worth knowing:
- Positioning that is not high enough. In one series, 30 of 31 transposed ovaries still received over 5 Gy because they had been placed below the iliac crest.
- Scattered radiation — even when well placed, the ovaries can receive 8-15% of the prescribed dose.
- Migration back into the pelvis, which is why the procedure should be done as close as possible to the start of radiotherapy.
- Torsion or vascular compromise, prevented by three-point fixation.
- Concurrent chemotherapy reduces the success rate to about 51%.
A scheduling point that many patients get wrong: in rectal cancer, radiotherapy comes before surgery. Consequently, a transposition performed during the resection plays no protective role — the radiation has already been delivered. Transposition has to be done as a separate laparoscopic procedure, before radiotherapy. It can, however, be combined with a staging laparoscopy, with the creation of a defunctioning stoma, or with harvesting ovarian tissue for freezing, under the same anaesthetic.
What is NOT a preservation method
GnRH analogues — the injections that “put the ovaries to sleep” — are not a fertility preservation method. The ASCO guideline is categorical: they should not be used in place of the established methods.
The evidence that exists comes almost exclusively from breast cancer, where the insult is chemotherapy. No study has evaluated these drugs in colorectal cancer. And, logically, there is no reason to believe that a hormone injection could protect an ovary receiving 44 Gy.
If you are offered “an injection that will protect your ovaries” as a substitute for transposition or for oocyte freezing, that is not guideline-concordant care.
How much treatment is actually delayed
This is the concern that most often blocks the decision — and it deserves to be weighed correctly.
Sperm freezing is measured in days. Ovarian transposition and ovarian tissue freezing, likewise. Oocyte freezing with a “random start” protocol takes about two weeks.
In practice, the interval between the colonoscopy biopsy and the first radiotherapy session already includes the staging MRI, the CT, the multidisciplinary team discussion and the planning CT. A preservation pathway of one to two weeks usually fits inside that interval without extending it — provided the referral is made promptly.
It has to be said honestly that the direct evidence for the oncological safety of this delay comes from breast cancer, not from rectal cancer; for rectal cancer there is no study that has measured it. There are, however, clear exceptions in which nothing is postponed: impending or established obstruction, significant gastrointestinal bleeding, other emergencies.
The asymmetry remains striking, though: the delay is measured in days or two weeks. The loss, if the window closes, is permanent and total.
The situation in Romania
Here I have to be direct about what I could not verify.
I could not find any official source confirming that fertility preservation for oncology patients is reimbursed in Romania. The existing national programmes — the Ministry of Health’s in vitro fertilization subprogramme and the Ministry of Labour’s voucher programme — are built around a diagnosis of infertility, not around preservation ahead of gonadotoxic treatment. Their criteria (body mass index between 20 and 25, ovarian reserve above a certain threshold) would in practice exclude many oncology patients even if they were otherwise eligible.
What certainly does exist: reproductive cell and tissue banks accredited by the National Transplant Agency, in Bucharest, Cluj, Constanta, Targu Mures and other cities. Some explicitly offer cryopreservation for oncology patients, including ovarian and testicular tissue. Costs are not published and should be assumed to be entirely private.
If you are in this situation, the practical steps are:
- Ask for a referral to an accredited assisted reproduction centre, before the first radiotherapy session
- Ask your radiation oncologist about the estimated dose to the ovaries or testicles and about the possibility of shielding
- If you are a woman, ask explicitly whether ovarian transposition before radiotherapy is feasible and whether the transposed ovary can be contoured as an organ at risk in the radiation plan
- Ask that the discussion and the decision be recorded in your medical notes
After treatment
Contraception is necessary during treatment and for about 3-6 months after the last dose, for men as well.
How long to wait before a pregnancy has no single answer. The European guideline recommends at least one year after chemotherapy. For men, the biological minimum is about 3 months, the length of one spermatogenesis cycle. Some authors recommend 2 years in colorectal cancer, because most recurrences occur in the first 2 years — but this is expert opinion, not evidence.
Pregnancy after rectal cancer is a high-risk pregnancy, and not because of the cancer. Population studies show higher rates of haemorrhage, caesarean section, premature birth and neonatal complications. Follow-up in a maternal-fetal medicine service, more frequent growth scans and planning of the delivery are all justified.
There is no evidence that pregnancy worsens the oncological prognosis after rectal cancer — but neither is there a study that has tested this directly.
For women operated on with an ileo-anal pouch, one concrete piece of good news: although natural fertility falls because of adhesions, in vitro fertilization success rates are similar to those of women who have not had surgery. A laparoscopic approach significantly reduces adhesions and shortens the time to pregnancy compared with open surgery.
What to take away
If you are under 50 and have rectal cancer, ask the fertility question at the first consultation, not at the third. Even if you are not sure you will want children. Even if nobody has raised the subject.
Counselling has value in itself, even when no procedure follows: patients who are counselled report a better sense of control and better quality of life. And those who are not counselled are often left with the regret of not having known they had an option.
The cost of a question is a few minutes. The cost of the question not asked can be permanent.
This article is for informational purposes only and does not replace medical consultation. Decisions about fertility preservation should be made together with your oncology team and a reproductive medicine specialist.
Key references: Su HI et al. Fertility Preservation in People With Cancer: ASCO Guideline Update. J Clin Oncol. 2025;43(12):1488-1515. — Ghanem S et al. Factors Associated With Premature Ovarian Insufficiency in Young Women With Locally Advanced Rectal Cancer Treated With Pelvic Radiation Therapy. Adv Radiat Oncol. 2021;6(6):100801. — Duffy A et al. Fertility Concerns Related to Surgery for Colorectal Cancer: An Under-Discussed Topic. Cancers. 2024;16(19):3376. — Tessier L et al. Laparoscopic ovarian transposition in anorectal malignancies: a systematic review and meta-analysis. Colorectal Dis. 2023. — ESHRE Guideline Group. ESHRE guideline: female fertility preservation. Hum Reprod Open. 2020;2020(4):hoaa052. — Stal J et al. Fertility Preservation Discussions Between Young Adult Rectal Cancer Survivors and Their Providers. Oncologist. 2022;27(7):579-586.